Generator regulating apparatus with diode



March 1, 1960 H. MITTAG 2,927,261

GENERATOR REGULATING APPARATUS WITH DIODE Filed Jan. 22, 1958 //V VENTOR na by:

GENERATOR REGULATING APPARATUS WITH DIODE Hermann Mittag, Stuttgart-Botnang, Germany, assiguor to Robert Bosch G.m.b.I-I., Stuttgart, Germany Application January 22, 1958, Serial No. 710,548 Claims priority, application Germany January 24, 1957 5 Claims. (Cl. 32225) The present invention relates to apparatus for antomatically regulating the voltage output of shunt generators, particularly for automotive vehicles. Regulating'devices of this type comprise a normally closed elec-v tromagnetic switch provided with a voltage coil and with a switching arm actuated in dependence of the voltage output, and also comprise a second normally open electromagnetic switch provided with at least one pair of contacts and with a current coil through which the generated current flows.

With this kind of regulating devices special measures have to be taken so that the generator voltage drops rapidly with increasing current if the load exceeds a value admissible for the particular generator. Therefore, additional electromagnetic switches have been added in the past to the standard apparatus, in order to influence the voltage and/or current coils accordingly. Such additional devices, however, make the regulating device more expensive and necessitate the use of substantially larger housings which is undesirable in view of the space restrictions applying to vehicles where such devices have to be mounted.

It is therefore a main object of this invention to provide for an apparatus of the type set forth which is much simpler in construction and therefore can be produced at lower cost.

It is another object of this invention to provide an apparatus for automatically regulating generators and comprising only a comparatively small number of substantially conventional elements.

It is still another object of the invention to provide an apparatus of the type set forth which is reliable in performance and convenient regarding maintenance.

With the above objects in view, an apparatus for antomatically regulating shunt generators, particularly for automotive vehicles, comprises, according to this invention, an electro-magnetically operated first regulator switch in circuit with the shunt exciting winding of the generator and movable between a first position in which the exciting current is permitted to increase, and a second position in which the exciting current is caused to decrease, including voltage-responding electro-magnetic means depending upon increasing voltage output of the generator for moving said first regulator switch into its second position; a second electro-magnetically operated switch in series between the generator and the load, and including a solenoid for operating this second switch be tween open and closed positions depending upon the output current flowing through this solenoid and this second switch; a variable conductor means connected in parallel with the solenoid coil of the second switch and having a substantially linear characteristic with a pronounced break at a point representing a critical voltagecurrent ratio, this conductor means being substantially non-conductive unless a potential difference larger than said critical voltage is applied to it, so that the conductor meansj is conductive only when the voltage drop,

United States Patent 0 2,927,261 Patented Mar. 1, 1

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under load, across the solenoid coil exceeds said critical voltage; and auxiliary means responding to that portion of the current output of the generator which flows through the conductor means when the latter are in conductive condition, and associated with the first-mentioned voltage-dependent electro-magnetic means for increasing the energization of the latter, whereby upon increase of the output current of the generator beyond a predetermined value the voltage output of the generator is automatically reduced and the output current substantially limited to said predetermined value.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will behest understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is an electrical diagram illustrating one embodiment of the invention; and

Fig. 2 is a diagram showing the VI characteristic of a component used in the embodiment illustrated by Fig. 1.

The regulating apparatus shown in Fig. 1 comprises two electromagnetic switches, the first of which has a voltage coil 10, a movable switching arm 11 and a stationary contact 12, while the other one comprises a cur rent coil 13, a movable switching arm 14 and a stationary contact 15. The switch arm 11 is normally urged into closed position by suitable means including gravity, or by a spring 11a. The switch arm 14 is urged, in a similar manner normally into its open position.

The movable switching arm 11 of the voltage-dependent switch is connected both to one end of the field winding 16 of a vehicle generator 17, as shown in Fig. l, and to a field resistor 18 connected in series with the field winding 16. One end of the voltage coil 10 is connected to electrical ground and thereby to the negative brush of the generator, while the other end of this winding is connected to the positive supply conductor 22a coming from the positive generator brush. The current coil 13 is connected in the positive supply line 22a between the positive brush of the generator and the stationary contact 15 of the second switch; when the switching arm 14 is moved into closed position, current is supplied via contact 15 to the battery 20 and possibly to other loads not shown in the circuit diagram. On the solenoid core (not shown) carrying the current coil 13 a second winding 21 made of a great number of turns of thin wire is arranged for providing a bias magnetization of the current coil 13 and polarizing same so that the switching arm 14 is moved into the open position away from contact 15 as soon as, owing to insufiicient generator voltage, a return current would flow from the battery 20 to the generator.

When the generator 17 is started and rotated at a sufiiciently high speed it is very quickly excited through the shunt-connected field winding 16 since during starting the switching arm 11 is held against contact 12, whereby the field resistor 18 is short-circuited. When the generator voltage reaches a value sufficiently high to produce a current in the voltage coil 10 capable of moving the arm 11 away from the contact 12, the field resistance 18 becomes operative, which drastically reduces the excitation current flowing through the field winding 16 and causes the generator voltage to drop accordingly until the latter reaches a preselected value at which the switching arm 11 cannot be held any more in its openposition against the effect of a spring 11a tending to move it to closed position, thus the switching arm 11 will return to its closed position and will again short-circuit the field resistor 18. The thus described process repeats regardless of whether the generator is working against the load formed by the current coil 13. The bias magnetization coil 21 and the associated armature, not shown in the drawing, engaging the movable switching arm 14, are adjusted in such away that the switching arm 14 is moved towards the stationary contact 15 as soon as the generator voltage exceeds that of the battery 20.

In order to prevent the generator from being overloaded due to high load currents, a diode 23 is connected, according to this invention, in a circuit 22 parallel to the current coil 13. An auxiliary winding 24 is connected in series with the diode 23; this winding 24 is mounted on an iron core, not shown in the drawing, which also serves as core of the voltage coil 10.

The diode 23 preferably consists of a semi-conducting germanium crystal which has, owing to a properly selected impurity, a characteristic (as shown in Fig. 2) with a pronounced bend or break at approximately 0.2 v. As long as the applied voltage U does not exceed the critical value of 0.2 v., the passing current I remains very weak, while it increases considerably in the area beyond the said voltage limit. Of course, any diode having a characteristic of the type shown by Fig. 2 could be used for the present purpose.

So as to adjust the apparatus for the maximum current permissible for the generator, the current coil 13 is dimensioned in a way to produce, at this maximum current, a voltage drop across the current coil 13 higher than the critical voltage at which the diode becomes fully conductive. The portion of the load current flowing now through the auxiliary winding 24 and the diode 23 produces an auxiliary energization of the first switch so as to support the effect of the voltage coil 14 owing to this additional energization the switching arm 11 is kept for a longer period in its open position, during its repeated opening and closing cycles, than would be the case corresponding to the actually prevailing generator voltage output. Consequently, conditions are simulated that correspond to a higher generator voltage than the existing one. The apparatus regulates, accordingly, the generator output to a voltage lower than the preselected value; this voltage output successively drops further if the load current keeps on increasing. The described embodiment shows, consequently, a characteristic which results, up to the mentioned load-current limit value, in a substantially constant generator voltage output but, from the said limit value on, in a steep drop of the generator voltage.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of regulating apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in apparatus for automatically regulating shunt generators, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist C1. the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, farily constitute essential characteristics of the generic or specific aspects of this invention and, therefore, suchadaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. In an apparatus for automatically regulating the voltage output of shunt generators, particularly for automotive vehicles, operating against a variable load, in combination, an electromagnetically operated first regulator switch in circuit with the shunt exciting winding of said generator and movable between a first position in which the exciting current is permitted to increase, and a second position in which the exciting current is caused to decrease, including voltage-responding electro-magnetic means depending upon increasing voltage output of said generator for moving said first regulator switch into said second position; a second electro-magnetically operated switch in series between said generator and said load, and including a solenoid coil for operating said second switch between open and closed positions depending upon said output current flowing through said solenoid and said second switch; a conductor means connected in parallel with said solenoid coil and having a substantially linear characteristic with a pronounced break at a point represent a critical voltage-current ratio, said conductor means being substantially non-conductive unless a potential difference larger than said critical voltage is applied to it so that said conductor means is conductive only when the voltage drop, under load, across said solenoid coil exceeds said critical voltage; and auxiliary means responding to that portion of said current output which flows through said conductor means when the latter are in conductive condition, and associated with said voltage-dependent clectro-magnetic means for increasing the energization of the latter, whereby upon increase of said output current of said generator beyond a predetermined value the voltage output of said generator is automatically reduced and the output current substantially limited to said predetermined value.

2. In an apparatus for automatically regulating the voltage output of shunt generators, particularly for automotive vehicles, operating against a variable load, in combination, a resistor in series connection with the shunt exciting winding of said generator for limiting the voltage output thereof; a normally closed first regulator switch including bias means for urging said switch into its closed position and being connected in parallel with said resistor for short-circuiting the latter when said switch is in closed position, and for reducing the exciting current when said switch is moved into its open position against the action of said bias means; voltage-dependent electro-magnetic means connected in parallel with said series combination of said shunt exciting winding and said resistor for moving said first regulator switch into its said open position when the voltage output of said generator reaches a value sutlicient to energize said electro-magnetic means for opening said first regulator switch; a normally open, electro-rnagnetically operable second switch connected in series between said generator and said load; a solenoid coil connected in series between said second switch and said generator for holding said second switch in closed position depending upon the current output of said generator flowing through said solenoid coil; a variable conductor means connected in parallel with said solenoid coil and having a substantially linear characteristic with a pronounced break at a point representing a critical voltage-current ratio, said conductor means being substantially non-conductive unless a potential difference larger than said critical voltage is applied to it so that said conductor means is conductive only when the voltage drop, under load, across said solenoid coil exceeds said critical voltage; and auxiliary means responding to that portion of said current output which flows through said conductor means when the latter are in conductive condition, and associated with said voltage-dependent electro-magnetic means for increasing the energization of the latter, whereby upon increase of said output current of said generator beyond a predetermined value the voltage output of said generator is automatically reduced and the output current substantially limited to said predetermined value.

3. An apparatus as set forth in claim 2, wherein said conductor means is a crystal diode.

4. An apparatus as set forth in claim 2, wherein said auxiliary means comprises an auxiliary solenoid coil con- 3 nected in series with said conductor means to form there- 2,707,263 with'a series-combination in parallel with said solenoid 2,760,140 operating said second switch, said auxiliary solenoid being 2,777,984 operativel y associated with said first regulator switch.

5. Anapparatus as set forth in claim 4, wherein said 5 15 392 conductor means is a crystal diode.

Umbarger et a1. Nov. 11, 1952 10 Jorgenson Apr. 26, 1955 Crumbliss Aug. 21, 1956 Menzel Ian. 15, 1957 FOREIGN PATENTS Australia Feb. 14, 1952 

